The present invention relates to an inkjet printer which injects ink particles in accordance with a drive waveform, and a drive method and drive device for same, and more particularly, an inkjet printer, and drive method and drive device for same, whereby a plurality of drive patterns are generated by combining drive waveforms within a single cycle.
Inkjet printers are used in recording devices for text, images, and the like, such as printers, copying machines, facsimile machines, and the like. Print data from a host PC is sent to the control section of an inkjet printer, and this control section sends waveform data (DRV), waveform selection data (SDATA), and the like, to a head drive section on a head carrier, and ink is injected from an ink jet head.
In such an inkjet printer, the size of the injected ink particle can be changed by means of the drive waveform. Therefore, if it is required to represent print density in an image, recording is performed by injecting several ink particles of different sizes from the same inkjet nozzle. The prior art is now described with reference to FIG. 12 and FIG. 13.
FIG. 12 is a compositional diagram of a conventional inkjet head drive circuit, and FIG. 13 is an illustrative diagram of a drive waveform thereof. As shown in FIG. 12, drive generators 94, 95, 96, 97 are provided in equal number to the number of types of ink size (in this diagram, there are four such types,) and these drive generators 94-97 are driven simultaneously. And a drive waveform for injecting a desired ink particle is selected by a waveform selector section 92, and the nozzle of the ink jet head 93 is driven.
In this method, only four types of waveform can be generated. However, as shown in FIG. 13(A), one cycle is divided into 5 parts, and drive source 94 generates a waveform of waveform number xe2x80x980xe2x80x99 wherein no ink particle is generated, whilst the drive sources 95, 96, 97 generate waveforms of waveform numbers xe2x80x981xe2x80x99, xe2x80x982xe2x80x99, xe2x80x983xe2x80x99 wherein an ink particle is generated.
Here, waveform number xe2x80x981xe2x80x99 is a waveform for generating a micro-particle by the waveform of one part of the divided time period, whereas if waveform numbers xe2x80x982xe2x80x99, xe2x80x983xe2x80x99 are selected in sequence, then a waveform for generating a small particle in two parts of the divided time period is obtained. This waveforms are generated by each of the waveform generators in sequence from the left-hand side. Thereupon, when the input data is divided into data for respective cycles, and supposing that the divided data for one cycle has the waveform number xe2x80x9801010xe2x80x99, it is possible to obtain the waveform shown in FIG. 13(B), and hence a waveform for generating two micro-particles can be generated.
If it is supposed that a waveform number xe2x80x9812323xe2x80x99 is generated by the controller 90, then the waveform shown in FIG. 13(C) can be obtained, and hence a waveform for injecting one micro-particle and two small particles is injected.
Thereby, by using four waveform generators, it is possible to generate a greater number of types of waveforms, and hence a print pattern having a large number of surface area tone gradations can be achieved by means of a small number of waveform generators.
In the prior art, the landing positions at which the dots are situated are determined by the print timing at which they are injected within one cycle of the drive waveform. Therefore, a problem results in that the print pattern in one cycle is fixed. In particular, when printing images, it is desirable to change the printing pattern in accordance with the content of the image, but in order to achieve this, it is necessary to change the image data.
It is an object of the present invention to provide an inkjet printer, and a drive method and drive device for same, for controlling the landing positions of the respective dots in one cycle, and thereby changing the print pattern for one cycle.
It is a further object of the present invention to provide an inkjet printer, and a drive method and drive device for same, for changing the print pattern in one cycle, without changing the print data.
It is yet a further object of the present invention to provide an inkjet printer, and a drive method and drive device for same for printing an optimum print pattern in accordance with the image contents.
In order to achieve these objects, the inkjet printer according to the present invention includes: an inkjet head which performs recording by moving in a main scanning direction of a recording medium and jetting ink particles; a drive waveform generating unit for generating drive waveforms for jetting the ink particles; and a head drive unit for selecting the drive waveforms and driving the inkjet head, in accordance with print data. The drive waveform generating unit generates a drive waveform for jetting ink particles having respectively different ink speeds within a unit cycle, said one ink particle is jetted in cycles each corresponding to one of the parts obtained by dividing the unit cycle by an integer.
In the present invention, by changing the speed of the ink particles injected in one cycle of a drive waveform, the landing position of each dot in one cycle is controlled and the dot pattern within one cycle can be changed. Since this is achieved by means of the drive waveforms, it can be implemented without changing the image data. Therefore, when printing images having low-resolution surface area tone gradations, in particular, it is possible to obtain sharper images by concentrating the landing positions of the dots and hence raising the resolution, if an image of sharp variation of density is required. Furthermore, if an image of smooth variation of density, such as a photograph, is required, then a smoother image can be obtained by dispersing the landing positions of the dots.
Moreover, in the present invention, the drive waveform generating unit generates a plurality of drive waveforms for jetting the ink particles of respectively different ink speeds within the unit cycle, in order to achieve different ink particle volumes, and therefore the diameter of the dots can be controlled, and the print pattern can be changed further.
Moreover, in the present invention, the drive waveform generating unit selectively generates the drive waveform and a second drive waveform for jetting the ink particles having the same ink speed, within the unit cycle, and hence the print pattern within a cycle can be selected.
Furthermore, the present invention further includes a control unit for controlling the generation of the second drive waveform and the generation of the drive waveform by the drive waveform generating unit, in accordance with instructions from an external source or analysis of the print data, and therefore a print pattern corresponding to the image to be printed can be selected.
Moreover, in the present invention, the drive waveform generating unit generates drive waveforms of different waveform shapes, within the unit cycle, and therefore the present invention can be achieved readily by changing the waveform shape.
Furthermore, in the present invention, the drive waveform generating unit generates drive waveforms having different voltage changing ratio, within the unit cycle, and therefore the ink speed of the ink particles can be changed readily.
Moreover, in the present invention, the drive waveform generating unit generates drive waveforms for concentrating the landing positions of the plurality of injected ink particles, within the unit cycle, and therefore, a sharp print image can be achieved, even in the case of an image of low resolution.
Furthermore, in the present invention, the drive waveform generating unit generates drive waveforms for dispersing the landing positions of the plurality of injected ink particles, within the unit cycle, and therefore, a soft image print result, such as a photograph, can be obtained.
Further objects and embodiments of the present invention will become evident from the following description of the embodiments and the accompanying drawings.